Remember, the key you have purchased is a prepaid code that is not compatible with the pre-installed software. This is an original Microsoft product.
Uninstall the previous version of Office that you have on your PC and restart your computer. This is important to avoid compatibility problems.
Download the desired version with the following download link:
Once the download is complete, follow these steps:
Deactivate your antivirus to run the downloaded installer (IMPORTANT STEP)
Right Click on the file and then select the option, "run as administrator"
You will get a warning pop-up (Don't worry it's a normal process), Click the YES Button
Finally, click on the "Install" button. This action unzips the application and will install your product
Once the download is complete and the installation of the program is complete, enter the activation key when running any application from the Microsoft Office package, it will be the first thing that will ask you.